Abstract: Silicon nanoparticles have potential application in so-called all-silicon optoelectronics or in biology as luminescent markers or optically controlled drug delivery. Silicon nanocrystals having 2-3 nm in size show visible luminescence due to the quantum confinement effect and organic (methyl) capping of the nanoparticles can enhance luminescence efficiency up to 20%. The native indirect bandgap of the silicon is in tensile-strained nanoparticles switched to direct bandgap behavior. By modifying the preparation conditions of the highly porous silicon we obtain hydrophilic nanoclusters suitable for biological research, however, the nanoparticles tend to agglomerate. Study of their toxicity showed better viability of the cells in comparison with diamond nanocrystals.

29.09.2016:

The generation and transport of energetic cosmic-ray particles (electrons, protons, ions) is among the most important problems in modern astrophysics. When the particles propagate in the cosmos, they often interact with turbulent magnetic fields. The resulting complicated evolution of the cosmic-ray distribution can be mathematically described as a simpler diffusive process. The diffusion approximation and its generalisations have been employed for studying the generation and propagation of energetic particles in many astrophysical situations: in the atmosphere of the Sun, interplanetary space, and the interstellar medium.

The VIP grant will support a systematic investigation of unresolved issues of particle transport in astrophysics, with a focus on analytical and numerical modelling of diffusive particle transport. The areas of particular interest are as follows. (1) Rigorous derivation of the diffusion and telegraph approximations for cosmic-ray transport modelling, which quantifies their accuracy. (2) Development of new analytical and numerical methods for solving the equations governing the transport of solar and galactic cosmic rays. (3) Critical examination of possible mechanisms of fractional particle diffusion in the cosmos.